Pellet quality of krill meal and pea protein containing diets and their sinking velocity at different water temperature and salinity
2025
Teshome Begashaw | Trond Storebakken | Mette Sørensen
Abstract The present study investigated the effects of replacing low‐temperature fishmeal (LT FM) with graded levels of partly deshelled Antarctic krill (Euphausia superba) meal and pea protein concentrate (PDKM + PPC), PDKM alone, or whole krill meal with shells (WKM) as primary protein sources on feed pellet physical quality and sinking velocity (Sv) under varying water temperatures and salinities. Seven experimental diets were formulated and tested for Sv (at water salinities of 20‰ and 34‰ and temperatures of 4, 12, and 20°C), along with pellet length, diameter, bulk density (BD), unit density (UD), apparent porosity (AP), and Ligno pellet durability index (PDI) at four testing times (30, 60, 90, and 120 s). Sv ranged from 8.1 to 12.4 × 10−2 ms−1across all test conditions and increased curvilinearly with PDKM + PPC inclusion, but significantly (p < 0.001) decreased when PDKM or WKM fully replaced LT FM. Lower salinity and higher water temperature increased Sv; across all diets and water temperatures, Sv was 4.2% higher at 20‰ salinity than at 34‰ salinity and increased by 0.52% per 1°C rise in water temperature. While pellet diameter decreased significantly (p < 0.001) with increasing PDKM + PPC, pellet length was largely unaffected. BD ranged from 561 ± 4 to 674 ± 5 kg m−3, UD from 899 ± 9 to 1039 ± 15 kg m−3, and PDI from 81.6% to 96.2%, with PDKM + PPC diets showing higher densities and better durability. Sv correlated significantly (p < 0.001) with UD (r = 0.811), BD (r = 0.817), and PDI (r = 0.918). Based on physical pellet quality results, diets containing a mixture of PDKM + PPC can be used up to 487 g kg−1 to produce a pellet with a Sv of 11.6 × 10−2 ms−1 irrespective of water salinity or water temperature.
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